Ordinary vehicles travel by taking the power out of an internal combustion engine using gasoline as fuel. Such vehicles have an on-board refrigeration circuit provided with a compressor driven by the internal combustion engine. Cooling is performed by evaporating refrigerant in an evaporator, and cooling the car interior air by the generated cold heat.
In addition, heating is performed by heating the car interior air with the heat of the cooling water used for cooling the engine.
Nonetheless, as such vehicles obtain power for driving through the combustion of gasoline or the like, the control or regulation of hazardous materials contained in the exhaust gas from the combustion has come to be zealously desired.
Moreover, conventionally, a refrigerant for cooling and refrigeration apparatus, for instance, chlorodifluoromethane (R22, boiling point 140.8° C.) or the like, has been used. However, R22 or the like have become the object of fluorine regulation, because they destroy the ozone layer by their high latency of ozone destruction, when they are released in the atmosphere and attain the ozone layer in the upper air of the Earth.
The destruction of this ozone layer is provoked by a chlorine group (Cl) in the refrigerant. Therefore, refrigerants not containing a chlorine group, for example, alternative refrigerants such as difluoromethane (HFC-32, R32, boiling point −52° C.) or the like, have been proposed; however, they have ended up being included in gases to be regulated by The 3rd Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change, Kyoto, 1997, because their Global Warming Potential (GWP) is 1300 to 1900, and their use has come to be difficult.
Given this trend of attaching importance to the environment, hydrocarbon system refrigerants such as propane, butane, i-butane, pentane, i-pentane, and natural refrigerants such as CO2 or others existing in the natural world and imposing less load to the environment have attracted attention, because they are free from an ozone layer destruction effect, combustibility or toxicity. Furthermore, they are extremely friendly to the environment, as their global warming potential (GWP) is 1, and in addition, they are economical.
Therefore, it has been proposed to use CO2 as a refrigerant for hybrid cars and idle stop coping cars that use electricity and gasoline as their energy source, or other vehicles, to perform the cooling by loading a refrigeration circuit provided with a compressor driven by electricity, and to perform the heating, on the other hand, by using the heat of the chilled water that is used to cool the engine.
FIG. 6 shows the composition of an on-vehicle air-conditioner for air-conditioning of the prior art, having, as necessary components, a refrigeration circuit 10, a cooling water circuit 20, and a damper apparatus 30 for controlling the flow of the car interior air.
The cooling water circuit 20 has a cooling water car exterior heat exchanger 21, also called a radiator, installed exterior to or outside of the car interior or passenger cabin, through which the cooling water circulates in order to cool an engine (not shown) such as an internal combustion engine. The cooling water circuit also has a cooling water car interior heat exchanger 22 installed at the car interior or passenger cabin side for exchanging heat between the car interior air and the cooling water, and a pump 23 for circulating cooling water among them, or the like.
The refrigeration circuit 10 is provided with a compressor 11 driven by an electric motor disposed in a closed vessel (not shown), a gas cooler (sometimes designated as a refrigerant car exterior heat exchanger) 12 for cooling the refrigerant compressed to a high pressure by the compressor 11, an expansion valve 13 for expanding the cooled refrigerant, an evaporator 14 for generating cold heat by vaporizing the refrigerant, a four-way valve 15 for flowing the refrigerant in the direction shown by the continuous line in the drawing or in the direction shown by the broken line, through switching-over.
In case of cooling by means of the refrigeration circuit 10, the four-way valve 15 is set to circulate the refrigerant as shown by the continuous line arrow. In this case, the refrigerant sucked by the compressor 11 is compressed to a high pressure, and the refrigerant compressed to the high pressure is cooled by the gas cooler 12 (refrigerant car exterior heat exchanger). The cooled refrigerant is then vaporized by the evaporator 14 via the expansion valve 13 for generating cold heat, and thereafter, sucked again by the compressor 11 via the four-way valve 15. The car interior air is delivered to the evaporator 14 by a fan (not shown), whereby the refrigerant exchanges heat with the car interior air, evaporates and returns to the compressor 11. As the heat for the evaporation of the refrigerant is transferred from the car interior air, the temperature of the car interior air is lowered by as much, thereby cooling the car interior.
It should be appreciated that, at this time, if the car interior air that has exchanged heat with the evaporator 14 is sent to the cooling water car interior heat exchanger 22, the temperature of the car interior air once cooled then elevates. Therefore, a damper apparatus 30 is moved to the position shown by the continuous line in order to prevent the car interior air from being sent to the cooling water car interior heat exchanger 22.
On the other hand, during the heating operation, the four-way valve 15 is set to circulate the refrigerant as shown by the broken line arrow. In this case, the refrigerant sucked by the compressor 11 is compressed to a high pressure, and the refrigerant compressed to the high pressure is sent to the evaporator 14 via the four-way valve 15. The refrigerant is then cooled using this evaporator 14 as a gas cooler. The cooled refrigerant is sent to the gas cooler 12 via the expansion valve 13. The refrigerant is vaporized using this gas cooler 12 as an evaporator (refrigerant car exterior heat exchanger) for generating cold heat, and thereafter, sucked again by the compressor 11 via the four-way valve 15. The car interior air is sent to the evaporator 14 used as a gas cooler by a fan (not shown), whereby the refrigerant exchanges heat with the car interior air to cool. As the heat during the refrigeration of the refrigerant is transferred to the car interior air, the temperature of the car interior air is elevated by as much, and the car interior is heated. Additionally, the pump 23 is driven at the same time as the vehicle is driven to circulate the cooling water, and heating by the cooling water circuit 20 is performed simultaneously.
By setting the damper apparatus 30 at the dashed line position, the car interior air is sent by a fan (not shown) and heated by the evaporator 14 used as a gas cooler. The heated car interior air is sent to the cooling water car interior heat exchanger 22 and heated again for performing the heating. Nonetheless, when the refrigeration circuit of such on-vehicle air-conditioner is used for heating during travel in winter or the like, frosting occurs on the refrigerant car exterior heat exchanger 12, and the performance of the refrigerant car exterior heat exchanger 12 deteriorates. Therefore, a defrosting operation is performed; however, there is a problem in that the defrosting can not be realized easily, because air at low temperature flows into the refrigerant car exterior heat exchanger.
In addition, when the refrigeration circuit of such an on-vehicle air-conditioner is used for cooling during traffic congestion during high temperature in summer or the like, there is a problem in that the cooling efficiency of the refrigerant car exterior heat exchanger 12 deteriorates due to the radiation heat of drivers such as the engine, motor or the like and the flow of hot air from one's vehicle, or the exhaust heat or the like of vehicles traveling ahead. The refrigerant ends up being cooled insufficiently, and the car interior cooling becomes unsatisfactorily.
Also, when the refrigeration circuit is used for cooling during summer or the like, in a vehicle having on board such on-vehicle air-conditioner for air-conditioning, there is a problem in that the cooling efficiency of the refrigerant car exterior heat exchanger 12 deteriorates and the refrigerant ends up being cooled insufficiently, if the refrigerant car exterior heat exchanger 12 is exposed to direct sunlight, and the car interior cooling becomes unsatisfactorily.
It is an object of the present invention to provide an on-vehicle air-conditioner for air-conditioning that can solve problems of the prior art, and perform effectively cooling, heating, defrosting or the like, even in the case of using, for example, CO2 as a refrigerant, in vehicles such as hybrid cars using electricity and gasoline as their energy source, idle stop coping cars or the like.